This is actually really easy to answer. Your first game off the bat should be Metal Gear Solid 2: Sons Of Liberty.
Finish the prologue chapter in the Tanker, then immediately switch over to Metal Gear Solid 4: Guns Of The Patriots.
Finish the first two chapters of MGS4 before starting Metal Gear Solid 3: Snake Eater.
Once the prologue Virtuous Mission in MGS3 is complete, you can now return to MGS2.

Complete the rest of MGS2, but when a certain character is revealed to be someone else, then start Metal Gear Solid 1.

During Metal Gear Solid 1, play normally until the first mention of the words 'Big Boss' are heard.
Then you must play Metal Gear 2: Solid Snake in its entirety.

Afterwards, complete MGS1, then finish MGS2. Finish Chapter 3 of MGS4 before moving on to Metal Gear Solid: Peace Walker.

After finishing 3 chapters of MGS: PW, get to the final boss fight of MGS3. Before defeating the final boss,
play the entirety of Metal Gear Solid: Portable Ops.
The overarching story of MGS: PO should be remembered, but you can ignore the finer details. Finish MGS3 after MGS: PO is finished.

Now go forward and finish Chapter 4 of MGS4 and MGS: PW, in that order. Once MGS: PW's fourth chapter is done,
play Metal Gear Solid V: Ground Zeroes's main story mission.
Optional missions can also be done, but ignore the extra mission Jamais Vu / Deja Vu for now.

Now go through Metal Gear Solid V: The Phantom Pain. After completing Chapter 1, go back and finish MGS: PW.
Then go through Chapter 2 and -- once finished -- immediately jump in and play Metal Gear.

Once Metal Gear is done, play Jamais Vu / Deja Vu, whichever one you want.
Now you must play the Metal Gear Ac!d series in chronological order, before finishing off the AU timeline with Snake's Revenge.

Now you're stuck in an alternate timeline. To get back to the main timeline and understand all angles of Hideo Kojimbo's master storytelling structure,
play through the Subspace Emissary of Super Smash Brothers Brawl until Solid Snake is unveiled.
When Solid Snake is unveiled, you must immediately go on YouTube and watch the Secret Theater for MGS3: Snake Eraser.

Finish Super Smash Brothers Brawl, then go on to finish MGS4. Afterwards, you can safely play Metal Gear Rising: Revengance and know literally everything there is to know about Metal Gear.
Just as Mr. Konjami intended it to be.